The primary goal of this project is to determine how and why specific responses become attached to specific stimuli and how well these learned connections transfer to stimuli and responses different from the ones occurring during initial learing. The project currently focuses on the phenomenon of sign-tracking, which involves the tendency of organisms(a) to orient toward, approach, and oftern contact localizable and reliable signals of imminent Pavlovian appetitive reinforcers (USs), and (b) to withdraw from signals of nonreinforcement. In this connection we are particularly studying (1) spatial, temporal, and "predictive" relations between CS, US, and intertrial intervals, (2) specific Properties of CS and US (localizability, modality), (3) the addition of various response-reinforcer contingencies, (4) the acquisition of various sign-reinforcer correlations in situations where S is physically prevented from contacting the sign or consuming the reinforcer (a version of latent learning), (5) several different species (rats,pigeon, duckling) and reinforcers (food, water, brain stimulation, imprinted object, electric shock), and (6) various response components and measures (orienting, approach-withdrawal, contact of CS and US). Experiments also examine the intimate role of sign-tracking in behavioral contrast and positive conditioned suppression. Findings indicate the dominance of sign-reinforcer over response-reinforcer correlations in controlling skeletal behaviors often regarded as controlled in "operant" fashion; they also cast doubt on the operant respondant distinction and seem to support Pavlov's views on stimulus substituion.